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Re: Patch for lookaround assertion in regexp


From: Stefan Monnier
Subject: Re: Patch for lookaround assertion in regexp
Date: Mon, 23 Jan 2012 12:11:26 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.92 (gnu/linux)

>> If it doesn't then it's a job for the translation layer. Char syntaxes
>> and categories could be converted into the standard [...] format.
> Enumerating the syntax/category members is not an option.

Indeed.

> There is no easy way to do that.

For `categories', there is a way, but the result is a *very* large [...]
chunk, so it's impractical.  For `syntax' there is indeed no way, since
the syntax of a char doesn't only depend on the char itself but also of
the `char-table' text-property that might be applied to that particular
character position (and of course, if we ignore this problem, we're
still back to the same problem of enormous [...] expressions, as is the
case for categories).
These entities really need to be implemented inside the regexp-engine
(but they're usually pretty easy to implement there).


        Stefan



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